This invention relates to blends of high acyl gellan gum and starch having textural and functional properties comparable to those of starch alone. This invention also relates to fast-gelling food products, made with the blends of the invention and at least one food ingredient, which have high shear-stability and low-rigidity. Also part of the invention are methods of preparing the native gellan and starch blends of the invention and gelled products containing the blends.
The estimated U.S. consumption of natural and modified thickening and gelling agents used as food additives in 1983 was about 313,000 metric tons, with an average annual growth rate of 3.5% projected for an estimated 1988 consumption of 370,000 metric tons. Starches represent about 70% of the total. Today, approximately 100,000 metric tons of 43% of the starch used in the food industry is modified. However, current trends in the market are to minimize the use of modified starches or to replace them with non-modified starches because modified starches are expensive. In addition, several suspect chemicals have been used in the production of modified food starches. Starch is the most commonly used material to thicken liquid edible solutions, especially foods. In a typical application, starch is mixed with water, heated to swell the starch granules, and solubilize amylose molecules, and the dispersion is cooled to form a gel or a paste.
Although chemically modified starches comprise a large portion of the starches used in the food industry, chemical modification (cross-linking) limits the swelling of the granules and produces starches which are more shear stable than unmodified starches. Chemical modification (substitution) also controls the way that amylose chains re-associate to form gels.
Other hydrocolloids such as carboxymethyl cellulose (CMC) and xanthan gum have been used to improve the starch paste texture and/or reduce the amount of starch used. However, these hydrocolloids usually also have a detrimental effect on the cook-up viscosity of the starch. Hydrocolloids have also been used to improve the shear stability of starches, and some, such as carrageenan, have proven effective. However, large amounts of carrageenan must be added to attain this effect.
A variety of starch derivatives are known in the art, and some are described below.
Thin boiling starches: These are starches produced by acid hydrolysis. Usually either hydrochloric or sulfuric acids are used the hydrolyze the starch. They do not swell as much upon cooking as raw starch, but become opaque and form rigid gels on cooling. These starches are useful in gum candies and in applications utilizing the film forming properties of starch.
Cross-linked starches: These starches can be produced with polyfunctional reagents, i.e., reagents which contain two or more reactive groups to form bridges between polymer chains within the starch granule. Food starches are usually cross-linked using reagents of the phosphate ester type (phosphorous oxychloride or sodium trimetaphosphate). The purpose is to prevent the starch granule from swelling beyond a certain point. Cross-linking acts mainly on the outer surface of the granule since it is done without gelatinizing the starch. This chemical bonding around the surface inhibits the breakdown or rupturing of the starch granule during processing. This, in turn, reduces the amount of amylose and amylopectin molecules in solution. Cross-linked starches eliminate the elastic or rubbery texture of regular or waxy maize gelatinized starches. They provide a desirable short smooth texture and reduce breakdown of viscosity in retorting of acidic food products. They provide thickening at lower concentrations and decreased shear breakdown in processing. Such starches, however, still suffer from problems of retrogradation since they do not bind water well. For this reason they are not freeze-thaw stable.
Acetate Modified Starches: Starch acetates are commonly prepared from acidic anhydride in an alkaline starch suspension at low temperatures. The resulting starch has a non uniform degree of substitution as more acetate groups are found on the outside of the granule than on the inside. These starches are considered more modified than the cross-linked starches. This modification reduces the amount of association between the starch chains after gelatinization. Small amounts of acetyl groups can eliminate the low temperature instability waxy maize cross-linked starches to give stability, texture and clarity in pie fillings, salad dressings and frozen foods. With regular starches (owing to the association of the amylose) the retrograded structure can be minimized to provide products with smooth uniform body. These products are more expensive to produce than native or simple cross-linked starches and are considered more radical than either of these.
Hydroxyalkyl Starches: Hydroxyalkyl starch ethers are produced from starch and an alkaline oxide. The modification is carried out at sub-gelatinization temperatures. This modification improves the "water binding" capacity of the starch. This modification is considered more radical than other chemical modifications to starch as many of the impurities remain after the modification is complete. These starches have been suspect due to these impurities. In addition, these starches are the most expensive to produce. Also, these starches usually require a higher use level to achieve a viscosity similar to a lesser modified or non-modified starch. Starch pastes of this modification tend to be more cohesive than simple cross-linked products. They are more clear and stable to low temperatures and they exhibit good freeze-thaw stability. In addition, the gelatinization temperature is usually lowered significantly. Both of the above described processes are under scrutiny by international regulatory agencies. As a result major food producers are seeking more natural or natural fundamental alternatives to these modifications.
Combinations of deacetylated and partially deacetylated gellan gum and starch are known in the art. For example, Baird, et al., Bio/Technology, page 781 (November 1983) disclose that it may be desirable to use gellan gum in combination with modified starches to obtain optional product texture and stability. Kang, et al., "Some Novel Bacterial Polysaccharides of Recent Development", page 240, disclose that gellan gum may be used as a structuring agent to replace or partially replace the starch. Sanderson et al., Food Technology, (April 1983) disclose: in Table 4, page 66, a starch jelly formulation containing 6.56% starch and 0.2% gellan gum; at page 68, FIG. 8 am amylograph for a 4.8% starch/0.2% gellan gum blend; and at page 68, the advantages of combining starch and gellan gum in pie fillings and puddings. U.S. Pat. No. 4,517,216, Table 1--1 discloses blends of 0.25% gellan gum and 0.25% corn starch. These blends contain higher amounts of gellan gum than the blends of this invention.
Accordingly, providing a blend of native or modified starch with low amounts of high-acyl gellan gum of reduced cost and equal or improved characteristics such as starch pastiness and flavor would be highly desirable.